Many processes and devices can be utilized for pressure sensing applications. Pressure sensors or pressure transducers can be used in a wide range of sensing applications. In many cases, it can be desirable to measure the pressure of fluid media such as water, fuel, oil, acids, bases, solvents and corrosive gases. The fluid media can also include, but is not limited to air, nitrogen, industrial process gases, water, automotive fluids, pneumatic fluids, coolants and industrial chemicals. For such applications, differential pressure sensors can be utilized for accurately sensing the pressure of the fluid media. Such differential pressure sensors can be made using well-known semiconductor technology. The most common differential pressure sensors can be solid-state silicon pressure sensors including a thin silicon diaphragm that is stressed in response to an applied pressure. The stress can be measured by piezoresistive elements formed in the silicon diaphragm. The measured stress can be calculated to measure the pressure of the fluid media.
In addition, the differential pressure sensors can incorporate a silicon pressure sensor die to exhibit a high degree of accuracy. The differential pressure sensors can also include two pressure ports in order to sense difference in pressure between the two ports for calculating the media pressure. Such differential pressure sensors typically require fluid media on both the top and bottom sides of the diaphragm in such a way that the diaphragm of the differential pressure sensor can come into contact with the media that can be corrosive or harmful. This corrosive or harmful media can damage other components of the pressure sensors, in particular bond pads that are exposed for wire bonding the differential pressure sensor to the package.
In many applications, the media can create a harsh environment for the exposed bond pads, which can results in long-term reliability failures. Therefore, the differential pressure sensors should preferably be constructed in such a way that it can be resistant to the media or be physically isolated from the media for measuring the media pressure. Thus, differential pressure sensors can either be inadequately protected for media compatibility or used with additional hardware that becomes prohibitively expensive for many applications. Hence, it would be desirable to isolate areas that could be damaged by media exposure such as the bond pads and wire bonds from direct contact with the media for reliable operation.
In some isolation arrangements of the differential pressure sensors, the environmentally sensitive silicon pressure die can be sandwiched between an elastomeric media seal and a conductive elastomeric pad contained within a housing. The pressure sensors can utilize the pre-molded elastomeric seals to separate the pressure die from a relatively harsh, wet, pressure sensing environment. Such pressure sensors can obtain true differential operation of the sensors and an accurate pressure of the media, but can increase production cost of the sensors.
In the majority of prior art, the differential pressure sensors can provide advance media isolation arrangements, but can require additional costs in construction of isolation sections. Thus, the manufacturing expense of pressure sensors can be increased and also, the accuracy of the pressure sensors can be reduced. It is highly desirable to provide a media compatible differential pressure sensor that can exhibit substantial advantages of reliability and performance without increasing the production costs over existing technologies.
A need therefore exists for an improved differential pressure sensor with high reliability, which can provide media isolated electrical connections that are ultimately more efficient and sturdier than presently implemented pressure sensors. Such differential pressure sensors are described in greater detail herein.